Temperature control system



Nov. 28, 1939. c GRANT 2,181,427

TEMPERATURE CONTROL SYSTEM Filed Jan. 2, 1956 FLOOR \NE.

. Arthur C. Grarzt it j M Patented Nov. 28, 1939 TEMPERATURE CONTROLSYSTEM Arthur C. Grant, St. Paul, Minn., assignor toMinneapolis-Honeywell Regulator Company, Minneapolis, Minn, acorporation of Delaware Application January 2, 1936, Serial No. 57,085

1 Claim.

My invention relates to an improvement in a temperaturecontrol system,and particularly to means for varying the operation of said system inaccordance with the difference in temperature 5 between two levels.

In the heating of buildings, considerable difficulty is experienced inthat the temperature at lower levels tends to be less than that athigherlevels. This tendency increases as the temperature outside the buildingfalls farther below that maintained inside the building. Thisdifferential in temperature between different levels depends to someextent upon the building characteristics, but for any particular type ofbuilding it is possible to determine a definite relationship betweenthis differential and the difference between outside and insidetemperatures.

The common practice is to locate a thermostat or other heat-responsivedevice at a point corresponding to. the normal breathing level. In suchan installation, the thermostat is usually adjusted so that an optimumtemperature, usually around 70, is maintained at the level at which thethermostat is located. As the temperature outside falls below thistemperature, the temperature adjacent to the floor also decreases. Ifthis temperature drop is suniciently great, the occupant of the room,especially if he be seated, will experience considerable discomfort. Ifthe thermostat is set so as to maintain a higher temperature, the roomwill be comfortable until the temperature outside again changes with theresultant change in the differential between breathing line and floorline temperatures. The tem- 'perature maintained will, however, be toohigh in mild weather and the result will be that the occupant becomesaccustomed to an excessively high temperature and there will be anunnecessary wastage of fuel.

An attempt has been made to overcome this difllculty by locating a.thermostat at an intermediate level. Such an arrangement isunsatisfactory since the differential in temperature between said levelsvaries. Thus, if the thermostat is adjusted so as to maintain atemperature lower than the optimum temperature at said intermediatelevel, the temperature at the breathing line level will be uncomfortablylow when there is only a slight differential in temperature between the50 two levels. If, on the other hand, the intermediately locatedthermostat is adjusted so as to maintain an optimum temperature at saidintermediate level, and the temperature outside be comes so low that thetemperature differential 55 becomes large, either the temperatureadjacent gagement therewith. The movement of said 5 the normal breathinglevel is too high or that adjacent the floor is too low, depending uponthe height at which the thermostat is located.

An object of the present invention is to provide means for automaticallyadjusting a thermostat located at the'normal level in accordance withthe variation in the differential between breathing line and floor linetemperatures.

A further object of the present invention is to provide a temperaturecontrol system in which 10 the point at which the temperature iscontrolled is shifted in accordance with the degree with which thebreathing line temperature differs from the temperature at the floorline level.

A further object of this invention is to provide 15 temperature controlmeans located at one level 'and responsive'to the temperature at saidlevel,

which means is automatically compensated by temperature responsive meanslocated at a second level. 00

,Further objects of the invention will be apparent from the accompanyingdescription and drawing, of which: Figure l is a diagrammatical view ofmy system shown as associated with a conventional heating plant, andFigure 2 is a 25 semi-diagrammatical view of an alternative form of mytemperature control system on a somewhat larger scale.

Referring to Figure 1 of the drawing, my temperature control system isshown as associated with a conventional heating plant I supplied with asuitable fuel, which for purposes of illustration may be gas, through apipe 2 controlled by an electrically operated valve 3. Said valve isconnected through conductors 4 and 5 with a suitas able source of power,not shown, in series with a temperature responsive device 6 whichcontrols the operation of said valve.

Said temperature responsive device 6, which is shown in the form of aconventional thermostat, is located at the breathing line- Hi. Itcomprises a bimetallic element 1, to which is attached a contact armadapted to engage with a contact .8. The bimetallic element is soconstituted as to cause said contact arm to move into engag'e- 5 mentwith said contact upon a fall in temperature in the space in which saidthermostat is located.

Associated with said thermostat is an electrical heating element 9supplied through conduc'tors l0 and H, with electrical current forheatingthe same. The flow of electrical current to said heating element9 is controlled by a resistance I! having a contact I in slidingencontact over said resistance I2 is controlled by a second heatresponsive element l3 located adjacent to the floor line level. Thisheat responsive element l3 comprises a bimetallic element which is soconstituted as to cause said contact M to move to the left upon thetemperature adjacent to the floor line falling.

The apparatus is adjusted so that when the temperature is uniformthroughout the room, thermostat 6 will control the action of the valvein the fuel supply means so as to cause an optimum temperature to bemaintained at the breathing line level. When the apparatus is soadjusted, contact M will be as far to the right upon resistance l2 as itwill be in normal operation. Under these conditions heating element 9will be supplied with the maximum amount of heat with which it issupplied during operation.

As the temperature falls outside with corresponding fall in temperatureadjacent to the floor line, thermo-responsive element l3 will causecontact Hi to be moved to the left with the result that more resistanceis introduced into the circuit so that less current is supplied toheating element 9. This will result in the contacts of thermostat 6remaining in engagement at a higher temperature than before, with theresult that a higher temperature is maintained at the breathing linelevel. The result of this increase in temperature at the breathing linelevel is that the optimum temperature now exists at some intermediatepoint between said breathing line level and floor line level. It willthus be seen that this increase in the temperature maintained at theupper level produces an effect similar to a physical lowering of theposition of the themestat 6. If the temperature outside should fallstill further with the resultant further decrease in the temperatureadjacent to the floor line level,-

heater 9 will be supplied with still less current and the temperature atwhich the contacts of the .thermostat separate is still further raised.Thus,

a still higher temperature will be maintained at the breathing linelevel and the eifective point of control will be shifted still lower. Itwill be readily seen that as the temperature adjacent to the floor lineagain rises, the temperature maintained adjacent the breathing linelevel will be correspondingly decreased.

While I have shown a bimetallic element for affecting the movement ofcontact l4 along resistance l2, it will be obvious that any othersuitable temperature responsive means could be employed. For example, anexpansible bellows element filled with a temperature-sensitive "fluidthermostat has a contact ,arm 27 engaging with a I contact 22 to close acircuit through conductors 25 and 26 to a fuel controlled valve in thesame manner as in the previously described species.

The spacing of contact arm 21 from contact 22 is adjusted by varying thetension on spring 20 by means of the screw 2|. Connected to saidexpansible bellows l9 by capillary tubing 23 is a bulb 2|. Said'bulb 24is located adjacent the floor and contains a volatile fluid, the vaportension of which varies in accordance with the temperature adjacent saidfloor. As this vapor tension varies, the bellows element I9 is expandedor contracted, thus shifting the thermostat at its pivot ll, to move arm21 farther from, or closer to, its contact 22.

The system isinitially adjusted as .in the preditions, thermostat i6 isadjusted so that it will maintain an optimum temperature at the level atwhich it is located. As the floor line temperature falls, the vaportension in bulb 24 will decrease with the result that thermostat I5 isshifted about pivot point I! and contact arm 21 is accordingly broughtinto closer engagement with contact 22. The result of this change inadjustment of the thermostat isthat the contact arm will remain inengagement with contact'22 at a higher temperature than before, with theresult that a higher temperature is maintained at the breathing linelevel. As in the preceding case,- the effect of this increase intemperature adjacent to the breathing line level is a lowering of thepoint at which the temperature is controlled.

It will be readily seen that I have provided a means whereby it ispossible to locate a thermostat at a level at which it is most desirableto normally maintain an optimum temperature, and still avoid thepresence of an uncomfortably low temperature adjacent the floor.temperature control system maintains a temperature which is comfortableadjacent the floor line, the temperature maintained is one which is alsocomfortable at the breathing line level. Moreover, as the differentialin temperature between said levels approaches a zero value, thethermostat at the breathing line level approaches normal operation.

While I have described two detailed embodiments of my invention, it willbe understood that these are merely for the purpose of illustration, andthat my invention is limited only by the scope of the appended claim.

I claim as my invention:

In a system for'controlling the temperature of a room, said temperaturetending to be lower at lower levels in the room, a fluid fuel firedfurnace for heating a fluid medium, means for circulating said fluidmedium through said room, a thermostat responsive to the temperature ofthe room air at the breathing line level, means controlled by saidthermostat for regulating the flow of fluid fuel to said furnace, acontinuously effective auxiliary heater having a variable resistance incircult therewith located adjacent said thermostat to vary the controlpoint thereof, and a second thermostat responsive to the temperature ofthe room air adjacent the floor and operative to vary said resistance.to decrease the heating effect of said auxiliary heater as thetemperature of the air adjacent the floor decreases.

. ARTHUR C. GRANT.

Although my

